JP2002237404A - Composite magnetic particles and powder for magnetic recording medium and magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide composite magnetic particles and powder for a magnetic recording medium having high strength, excellent surface smoothness, and low light transmittance. SOLUTION: The surfaces of the composite magnetic particles and powder are coated with an organosilane compound or polysiloxane produced from alkoxysilane, and a phthalocyanine pigment is adhered to at least a part of the coated area. The composite magnetic particles and powder have a mean particle diameter of 0.02-0.70 μm and the mass of deposit per unit area of the phthalocyanine pigment to 100 wt.% magnetic particles and the power is adjusted to 1-100 wt.%. The magnetic recording medium uses the composite magnetic particles and powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION An object of the present invention is to provide a composite magnetic particle powder for a magnetic recording medium having excellent strength and surface smoothness and low light transmittance.

[0002]

2. Description of the Related Art In recent years, as long-term recording and miniaturization of video and audio magnetic recording / reproducing devices have progressed, the performance of magnetic recording media such as magnetic tapes and magnetic disks has been improved. There is an increasing demand for higher performance, higher output characteristics, especially improved frequency characteristics, and lower noise.

In particular, the demand for high-density recording of video tapes is increasing, and the frequency of a carrier signal to be recorded is higher than that of conventional video tapes. That is, it has shifted to the short wavelength region, and as a result,
The magnetization depth from the surface of the magnetic tape is extremely shallow.

In order to improve the output characteristics of a magnetic recording medium, especially the S / N ratio, for a short wavelength signal, it is necessary to reduce the size of the magnetic particle powder, reduce the thickness of the magnetic recording layer, and improve the magnetic particle powder. High dispersion and smoothness of the magnetic coating surface are required.

In order to make the magnetic recording layer thinner, it is necessary to improve the strength and durability of the magnetic recording medium.

This fact is described in Japanese Unexamined Patent Publication No. Hei 5-298679, entitled "... In recent years, with the development of magnetic recording, there has been an increasing demand for high image quality and high sound quality. Of fine particles and high density
Further, it is required to reduce noise and increase C / N by smoothing the surface of the magnetic tape. ... However, as the friction coefficient of the contact between the magnetic layer and the device system increases while the magnetic tape is running, the magnetic layer of the magnetic recording medium is likely to be damaged or the magnetic layer will be peeled off in a short time use. There is. Particularly, in the case of a video tape, since the video head and the magnetic recording medium run while contacting each other at a high speed, the ferromagnetic powder tends to fall off the magnetic layer, which causes clogging of the magnetic head. Therefore, it is desired to improve the running durability of the magnetic layer of the magnetic recording medium. .. ".

In order to improve the durability of the magnetic recording medium itself,
Oxide particles such as alumina are added to the magnetic layer as an abrasive. However, it is known that alumina has poor dispersibility, and when added in a large amount, causes a dropout and decreases the surface smoothness of a magnetic recording medium. Therefore, there is a need for a magnetic particle powder capable of maintaining the durability of a magnetic recording medium even when the amount of an abrasive such as alumina is reduced.

On the other hand, as the thickness of the magnetic recording layer is reduced, non-magnetic particles such as matite particles are dispersed in a binder resin into needle-like particles on a non-magnetic support such as a base film. By providing at least one underlayer (hereinafter, referred to as a "nonmagnetic underlayer"), it has been proposed and put to practical use to solve problems such as deterioration of the surface properties of the magnetic recording layer and deterioration of the electromagnetic conversion characteristics. (JP-B-6-93297, JP-A-62-159338, JP-A-63-159297)
187418, JP-A-4-167225,
JP-A-4-325915, JP-A-5-73882, JP-A-5-182177).

However, a magnetic recording medium having a magnetic recording layer provided on a non-magnetic underlayer has a problem that the surface smoothness is improved but the durability is poor.

This fact is described in Japanese Patent Application Laid-Open No. 5-182177, which states that "... a non-magnetic thick undercoat layer is provided on the surface of the support and then the magnetic layer is provided as the upper layer. Although the influence of roughness can be eliminated, there is a problem that head wear and durability are not improved, because conventionally, since a thermosetting resin is used as a binder as a non-magnetic lower layer, the lower layer hardens. The reason is that friction between the magnetic layer and the head and contact with other members are performed in an unbuffered state, and that the magnetic recording medium having such a lower layer is somewhat less flexible. It can be considered .... ".

Therefore, even when a magnetic recording layer is provided on a non-magnetic underlayer, the strength and durability of the magnetic recording medium can be maintained.
There is a need for improved magnetic particle powders for magnetic recording.

By the way, at present, the determination of the end of a magnetic tape of a magnetic recording medium such as a video tape is performed by detecting a portion of the magnetic recording medium having a high light transmittance by a video deck. If the light transmittance of the entire magnetic recording layer increases with the thinning of the magnetic recording medium, it becomes difficult to detect the end of the tape by the video deck.
The light transmittance is reduced by adding carbon black fine particle powder or the like to the magnetic recording layer, and the addition of the carbon black fine particle powder or the like to the magnetic recording layer is essential in current video tapes.

However, the addition of a large amount of nonmagnetic carbon black fine particles or the like not only hinders high-density recording but also hinders thinning. In order to reduce the magnetization depth from the surface of the magnetic tape and to further reduce the thickness of the magnetic tape, it is strongly required to reduce the amount of non-magnetic particles such as carbon black particles added to the magnetic recording layer as much as possible. Have been.

[0014] Therefore, there is a demand for magnetic particle powder for a magnetic recording medium which can reduce the light transmittance even if the amount of carbon black fine particle powder added to the magnetic recording layer is reduced.

Conventionally, in order to reduce the amount of carbon black fine particle powder added to the magnetic recording layer and to reduce the light transmittance of the magnetic recording layer, the surface of the magnetic particle powder is added to 100 parts by weight of the magnetic particle powder. It is known to use magnetic particle powder to which 0.5 to 10 parts by weight of carbon black is attached (Japanese Patent Laid-Open No. 2000-3640).
4, JP-A-2000-138115, JP-A-2
JP-A-2001-2424, JP-A-2001-2425, JP-A-2001-15317, JP-A-2001
No. 15318).

[0016]

A magnetic particle powder which is excellent in strength and surface smoothness and which can provide a magnetic recording medium having a small light transmittance is at the most demanded at present. A sufficiently satisfying magnetic particle powder has not yet been obtained.

That is, JP-A-2000-36404, JP-A-2000-138115 and JP-A-2001
JP-A-2424, JP-A-2001-2425, JP-A-2001-15317, JP-A-2001-153
No. 18, the magnetic particle powder described in each gazette,
Because carbon black is attached to the particle surface, the light transmittance and the dispersibility are improved, but as shown in the comparative examples described below, the resin adsorption strength is not sufficient, so
When used as a magnetic particle powder for a magnetic recording medium, the strength of the obtained magnetic recording medium is hardly sufficient.

Accordingly, the present invention provides a magnetic particle powder capable of obtaining a magnetic recording medium which is excellent in strength and durability and can reduce light transmittance by increasing the resin adsorption strength of the magnetic particle powder. This is a technical issue.

[0019]

The above technical object can be achieved by the present invention as described below.

That is, the present invention relates to an average particle size comprising magnetic particle powder in which an organosilane compound or polysiloxane formed from alkoxysilane is coated on the particle surface, and a phthalocyanine pigment is attached to at least a part of the coating. 0.02 to 0.70 μm composite magnetic particle powder, wherein the amount of the phthalocyanine pigment attached is 1 to 100 parts by weight based on 100 parts by weight of the magnetic particle powder. It is a composite magnetic particle powder (Invention 1).

Further, in the present invention, the particle surface of the magnetic particle powder of the present invention 1 is made of at least one kind previously selected from aluminum hydroxide, aluminum oxide, silicon hydroxide and silicon oxide. A composite magnetic particle powder for a magnetic recording medium, which is coated with an intermediate coating (the present invention 2).

Further, according to the present invention, the particle surface is coated with an organosilane compound or polysiloxane formed from alkoxysilane, and the coating is coated with carbon black, and further formed on the carbon black from alkoxysilane. A composite magnetic particle powder having an average particle diameter of 0.02 to 0.70 μm, comprising a magnetic particle powder coated with an organosilane compound or a polysiloxane, and a phthalocyanine pigment adhered to at least a part of the coating, A composite magnetic particle powder for a magnetic recording medium, wherein the amount of the phthalocyanine pigment attached is 1 to 100 parts by weight based on 100 parts by weight of the magnetic particle powder (Invention 3).

Further, in the present invention, the particle surface of the magnetic particle powder of the present invention 3 is made of at least one kind selected in advance from aluminum hydroxide, aluminum oxide, silicon hydroxide and silicon oxide. A composite magnetic particle powder for a magnetic recording medium, which is coated with an intermediate coating (the present invention 4).

The present invention also relates to a magnetic recording medium comprising a non-magnetic support, a magnetic recording layer containing a magnetic particle powder formed on the non-magnetic support and a binder resin, wherein the magnetic particle powder is a magnetic recording medium. A magnetic recording medium characterized by being the composite magnetic particle powder of any one of the present invention 1 to the present invention 4 (the present invention 5).

The present invention also provides a non-magnetic support, a non-magnetic underlayer containing non-magnetic particle powder and a binder resin formed on the non-magnetic support, and a non-magnetic under layer formed on the non-magnetic under layer. A magnetic recording medium comprising a magnetic recording layer containing particle powder and a binder resin, wherein the magnetic particle powder is the composite magnetic particle powder according to any one of the first to fourth aspects of the present invention. (The present invention 6).

The structure of the present invention will be described in more detail as follows.

First, the composite magnetic particle powder for a magnetic recording medium according to the present invention will be described.

In the composite magnetic particles of the present invention, the surface of the magnetic particles as core particles is coated with an organosilane compound or polysiloxane formed from alkoxysilane, and a phthalocyanine pigment is attached to the coating. It is a composite magnetic particle powder having an average particle size of 0.02 to 0.70 μm.

The particle shape of the magnetic particles as the core particles in the present invention is needle-like particles, spindle-like particles, rice-like particles, and plate-like particles.

The magnetic particle powder, which is the core particle powder in the present invention, includes maghemite particle powder (γ-Fe ₂ O ₃ ) and magnetite particle powder ( Fe
O _x .Fe ₂ O ₃ , 0 <x ≦ 1) Cobalt-coated magnetic iron oxide particles obtained by coating Co or Co and Fe on magnetic iron oxide particles, such as cobalt-coated magnetic iron oxide Co, Al, Ni, P, Zn, S other than Fe
i, B, cobalt-coated magnetic iron oxide particles containing different elements such as rare earth metals, metal magnetic particles containing iron as a main component, Co, Al, Ni, P, Zn, S other than iron
Iron alloy magnetic particles containing i, B, rare earth metal, etc., and the plate-like magnetic particles include Ba, Sr or B
Plate-like magnetoplumbite-type ferrite particles containing a-Sr and Co, N
i, Zn, Mn, Mg, Ti, Sn, Zr, Nb, C
and plate-like magnetoplumbite-type ferrite particles containing one or more coercive force reducing agents selected from divalent and tetravalent metals such as u and Mo. In the present invention, unless otherwise specified, both “needle-like particles” and “plate-like particles” are included.

In consideration of recent high-density recording of magnetic recording media, acicular metal magnetic particles containing iron as a main component and Co, Al, Ni, P, Zn, Si, B, rare earth metals other than iron And the like are preferable.

Considering the blackness of the obtained composite magnetic particle powder, the particle surface of the magnetic particle powder is coated with an organosilane compound or polysiloxane formed from alkoxysilane, and carbon black adheres to the coating. Magnetic particles are preferred.

The coating amount of the organosilane compound or polysiloxane of the magnetic particle powder in which carbon black is adhered to the surface of the magnetic particle via an organosilane compound or polysiloxane formed from alkoxysilane is determined based on the organosilane compound-coated magnetic particle powder, Alternatively, 0.02 to 5.0 in terms of Si with respect to the polysiloxane-coated magnetic particle powder.
%, And the amount of carbon black attached is 0.5 to 10 parts by weight based on 100 parts by weight of the magnetic particle powder.

The adhering carbon black may be either a carbon black layer or a partially adhering carbon black layer. Even if the alkoxysilane or polysiloxane is partially exposed, the phthalocyanine-based pigment may be used. An adhesion process can be performed.

The average particle diameter (average major axis diameter) of the magnetic particle powder having an acicular particle shape (hereinafter referred to as “acicular magnetic particle powder”) is 0.02 to 0.70 μm, preferably 0.1 to 0.70 μm. 03 to 0.60 μm, more preferably 0.04 to
The axial ratio (the ratio between the average major axis diameter and the average minor axis diameter) (hereinafter referred to as “axial ratio”) is 2.0 to 20.0 μm.
Is more preferable, More preferably, it is 2.5-18.0, Still more preferably, it is 3.0-15.0.

When the average particle size exceeds 0.70 μm, the obtained composite magnetic particles also become coarse particles,
When a magnetic recording layer is formed by using this, the surface smoothness of the coating film tends to be impaired. Average particle size is 0.02μm
In the case where the particle size is less than 1, since aggregation is likely to occur due to an increase in intermolecular force due to finer particles, uniform coating treatment on the particle surface of the acicular magnetic particle powder with alkoxysilane or polysiloxane and uniform coating treatment with phthalocyanine pigment Adhesion treatment becomes difficult.

When the axial ratio is more than 20.0, the entanglement of the particles increases, and uniform coating treatment with the alkoxysilane or polysiloxane and uniform adhesion with the phthalocyanine pigment onto the particle surface of the acicular magnetic particle powder. Processing becomes difficult. When the axial ratio is less than 2.0, the coating strength of the obtained magnetic recording medium decreases.

The average particle size (average plate surface diameter) of the magnetic particle powder having a plate-like particle shape (hereinafter referred to as “plate-like magnetic particle powder”) is 0.02 to 0.20 μm, preferably 0.1 to 0.20 μm. 025 to 0.20 μm, more preferably 0.03 to
0.20 μm, and the plate ratio (the ratio between the average plate surface diameter and the average thickness) (hereinafter referred to as “plate ratio”) is 2.0 to 20.
0 is preferable, more preferably 2.5 to 15.0, and still more preferably 3.0 to 10.0.

The average particle diameter of the plate-like magnetic particles is 0.20
If it exceeds μm, the obtained composite magnetic particle powder also becomes coarse particles, and when this is used to form a magnetic recording layer, the surface smoothness of the coating film tends to be impaired. 0.0
When the particle diameter is less than 2 μm, aggregation tends to occur due to an increase in intermolecular force due to the formation of fine particles. It becomes difficult to perform a proper adhesion treatment.

When the plate ratio exceeds 20.0, stacking between particles increases, and the surface of the plate-like magnetic particle powder is uniformly coated with alkoxysilane or polysiloxane and uniformly coated with a phthalocyanine pigment. It becomes difficult to perform a proper adhesion treatment. If it is less than 2.0, the coating strength of the obtained magnetic recording medium will be low.

The geometric standard deviation of the particle diameter of the magnetic particles is preferably 2.0 or less, more preferably 1.9 or less, and even more preferably 1.8 or less. When the geometric standard deviation value exceeds 2.0, uniform dispersion is hindered by the existing coarse particles, so that the surface of the magnetic particle powder is uniformly coated with alkoxysilane or polysiloxane and the phthalocyanine pigment is used. Makes it difficult to perform uniform adhesion treatment. The lower limit of the geometric standard deviation value is 1.01, and a value less than 1.01 is difficult to obtain industrially.

The BET specific surface area of the magnetic particles is 15 to
200 m ² / g is preferred, and more preferably 20 to 15
0 m ² / g, even more preferably 25-100 m ² / g
It is. When the BET specific surface area value is less than 15 m ² / g, the core particle powder is coarse or particles are sintered between particles, and the resulting composite magnetic particle powder is also coarse particles. When the magnetic recording layer is formed by using this, the surface smoothness of the coating film tends to be impaired. BE
When the T specific surface area value exceeds 200 m ² / g, aggregation tends to occur due to an increase in intermolecular force due to finer particles, so that a uniform coating treatment of the magnetic particle powder surface with alkoxysilane or polysiloxane is performed. In addition, it becomes difficult to perform a uniform adhesion treatment with a phthalocyanine pigment.

The blackness of the magnetic particles usually has a lower limit of L ^* value of more than 18.0 and an upper limit of 34.0, preferably 33.0. If the L ^* value exceeds 34.0,
Lightness is increased, and composite magnetic particles having sufficient blackness cannot be obtained.

Regarding the blackness of the magnetic particle powder to which the carbon black is adhered, the lower limit of the L ^* value is 15.0 and the upper limit is 27.0, preferably 26.0.

The resin adsorption strength of the magnetic particle powder is usually 60
% Or less.

The magnetic properties of the magnetic particles are as follows.
9.8 to 318.3 kA / m (500 to 4000 Oe)
Is preferred, and preferably 43.8 to 318.3 kA / m.
(550-4000 Oe) and the saturation magnetization value is 35
~170Am a ^{2 / kg (35~170emu / g)} , preferably 40~170Am ² / kg (40~1
70 emu / g).

When the magnetic particles are cobalt-coated acicular iron oxide magnetic particles, the coercive force value is 39.8 to 135.3.
kA / m (500 to 1700 Oe) is preferable, and 43.8 to 135.3 kA / m (550 to 17) is more preferable.
00 Oe), and the saturation magnetization value is 60 to 90 Am ² /
kg (60~90emu / g), more preferably ^{65~90Am 2 / kg (65~90emu / g} )
It is. In the case of acicular metal magnetic particle powder containing iron as a main component and acicular iron alloy magnetic particle powder, the coercive force value is 63.7 to 2
78.5 kA / m (800 to 3500 Oe) is preferable, and more preferably 71.6 to 278.5 kA / m (9
00-3500 Oe), and the saturation magnetization value is 90-1.
^{70Am 2 / kg (90~170emu / g} ) , more preferably 100~170Am ² / kg (10
0 to 170 emu / g). In the case of plate-like magnetoplumbite type magnetic particles, the coercive force value is 39.8-31.
8.3 kA / m (500 to 4000 Oe) is preferable,
More preferably, 51.7 to 318.3 kA / m (650)
４4000 Oe), and the saturation magnetization value is 35 to 70 Am
² / kg (35-70 emu / g) is preferred, and more preferably 40-70 Am ² / kg (40-70 emu / g).
g).

The coating according to the present invention comprises an organosilane compound (hereinafter referred to as an "organosilane compound") formed from the alkoxysilane represented by the chemical formula (1), a polysiloxane represented by the chemical formula (2), and a chemical formula represented by the chemical formula (3). Modified polysiloxane, a terminally modified polysiloxane represented by Chemical Formula 4, or a mixture thereof.

[0049]

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As the alkoxysilane, specifically,
Methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, diphenyldiethoxysilane, dimethyldimethoxysilane, methyltrimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, isobutyltrimethoxysilane, decyltrimethoxysilane, etc. Can be

In consideration of the adhesion effect and desorption rate of the phthalocyanine pigment, an organosilane compound formed from methyltriethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, isobutyltrimethoxysilane, and phenyltriethoxysilane is preferable. Organosilane compounds formed from triethoxysilane, methyltrimethoxysilane, and phenyltriethoxysilane are more preferred.

[0052]

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[0053]

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[0054]

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In consideration of the adhesion effect and the desorption rate of the phthalocyanine pigment, a polysiloxane having a methylhydrogensiloxane unit, a polyether-modified polysiloxane, and a terminal carboxylic acid-modified polysiloxane having a terminal modified with a carboxylic acid are preferred.

The coating amount of the organosilane compound or polysiloxane is determined based on the organosilane compound-coated magnetic particle powder,
Alternatively, the content is preferably 0.02 to 5.0% by weight, more preferably 0.03 to 4.0% by weight, more preferably 0.03 to 4.0% by weight in terms of Si, based on the polysiloxane-coated magnetic particle powder. 05 to 3.0% by weight.

If the amount is less than 0.02% by weight, it is difficult to attach 1 part by weight or more of the phthalocyanine pigment to 100 parts by weight of the magnetic particles. 5.0% by weight
If it exceeds 100, 1 to 100 parts by weight of the phthalocyanine pigment can be adhered to 100 parts by weight of the magnetic particle powder, so that there is no point in coating more than necessary.

The phthalocyanine pigment in the present invention comprises
Organic blue pigments such as metal-free phthalocyanine blue, phthalocyanine blue (copper phthalocyanine), and fast sky blue (sulfonated copper phthalocyanine) and organic green pigments such as phthalocyanine green, when the blackness of the resulting composite magnetic particles is considered It is preferable to use an organic blue pigment, more preferably phthalocyanine blue.

The amount of the attached phthalocyanine pigment is 1 to 100 parts by weight based on 100 parts by weight of the magnetic particle powder.

When the amount is less than 1 part by weight, it is difficult to obtain composite magnetic particles having sufficient blackness and resin adsorption strength because the amount of the phthalocyanine pigment attached is insufficient. When it exceeds 100 parts by weight, the obtained composite magnetic particle powder has a sufficient resin adsorption strength,
Since the amount of the phthalocyanine pigment attached is large, the phthalocyanine pigment is easily detached, and as a result, the dispersibility in the vehicle during the production of the magnetic paint may decrease.

The particle shape and particle size of the composite magnetic particle powder according to the present invention greatly depend on the particle shape and particle size of the magnetic particle powder as the core particle powder, and have a particle morphology similar to the core particle powder. And has a particle size slightly larger than the core particles.

That is, the composite magnetic particle powder according to the present invention comprises:
When needle-shaped magnetic particles are used as the core particles, the average particle diameter (average major axis diameter) is 0.02 to 0.70 μm, preferably 0.03 to 0.60 μm, and more preferably 0.04 to 0.70 μm.
0.50 μm, and the axial ratio is 2.0 to 20.0, preferably 2.5 to 18.0, more preferably 3.0 to 1
5.0.

When the average particle diameter of the composite magnetic particles exceeds 0.70 μm when the acicular magnetic particles are used as the core particles, the composite magnetic particles become large particles, and the magnetic recording layer is formed by using the particles. When formed, the surface smoothness of the coating film tends to be impaired. When the average particle diameter is less than 0.02 μm, aggregation tends to occur due to an increase in intermolecular force due to finer particles, so that dispersibility in a vehicle at the time of producing a magnetic coating material is reduced.

When the axial ratio exceeds 20.0, the entanglement of the particles increases, and the dispersibility in the vehicle during the production of the magnetic paint may become poor or the viscosity may increase. When the axial ratio is less than 2.0, the coating strength of the obtained magnetic recording medium decreases.

Further, the composite magnetic particle powder according to the present invention comprises:
When plate-like magnetic particles are used as the core particles, the average particle diameter (average plate surface diameter) is 0.02 to 0.20 μm, preferably 0.025 to 0.20 μm, and more preferably 0.03 to 0.20 μm.
0.20 μm, and the plate ratio is 2.0 to 20.0, preferably 2.5 to 15.0, more preferably 3.0 to 1
0.0.

When the average particle diameter of the composite magnetic particles exceeds 0.20 μm when the plate-like magnetic particles are used as the core particles, the composite magnetic particles become large particles, and the magnetic recording layer is formed by using the particles. When formed, the surface smoothness of the coating film tends to be impaired. When the average particle diameter is less than 0.02 μm, aggregation tends to occur due to an increase in intermolecular force due to finer particles, so that dispersibility in a vehicle at the time of producing a magnetic coating material is reduced.

When the tabular ratio exceeds 20.0, the stacking between particles increases, and the dispersibility in the vehicle during the production of the magnetic paint may become poor or the viscosity may increase. When the plate ratio is less than 2.0, the strength of the coating film of the obtained magnetic recording medium decreases.

The geometric standard deviation of the particle diameter of the composite magnetic particles is preferably 2.0 or less. If it exceeds 2.0, it is not preferable because the existing coarse particles adversely affect the surface smoothness of the coating film. Considering the surface smoothness of the coating film, it is preferably 1.9 or less, more preferably 1.
8 or less. In consideration of industrial productivity, the lower limit of the geometric standard deviation of the particle diameter of the composite magnetic particle powder is 1.01.
And those less than 1.01 are difficult to obtain industrially.

The BET specific surface area of the composite magnetic particles was 1
5 to 200 m ² / g is preferable, and more preferably 20 to 200 m ² / g.
150 m ² / g, even more preferably 25-100 m ²
/ G. When the BET specific surface area value is less than 15 m ² / g, the composite magnetic particle powder is coarse or the particles are sintered between the particles, and the magnetic recording layer is formed using the particles. In this case, the surface smoothness of the coating film tends to be impaired. When the BET specific surface area exceeds 200 m ² / g, aggregation tends to occur due to an increase in intermolecular force due to finer particles, so that dispersibility in a vehicle at the time of manufacturing a magnetic coating material is reduced.

Regarding the blackness of the composite magnetic particles according to the present invention, the lower limit of the L ^* value is 16.5, the upper limit is 24.0, preferably 23.0, and more preferably 22.0. L
^{* If the} value exceeds 24.0, the lightness increases and it is difficult to say that the blackness is excellent.

In the composite magnetic particles according to the present invention, when the magnetic particles to which carbon black is attached are used as the core particles, the lower limit of L ^* value is 14.5, and the upper limit is 21. 0, preferably 20.5, more preferably 20.
0.

The desorption rate of the phthalocyanine pigment from the composite magnetic particles according to the present invention is preferably 20% or less, more preferably 10% or less. When the desorption rate of the phthalocyanine pigment exceeds 20%, uniform dispersion in the vehicle may be hindered by the desorbed phthalocyanine pigment during the production of the magnetic paint.

The resin adsorption strength of the composite magnetic particle powder according to the present invention is at least 70%, preferably at least 72%, more preferably at least 74%.

The magnetic properties of the composite magnetic particles according to the present invention are as follows. The coercive force value is 39.8 to 318.3 kA / m (500
To 4000 Oe), more preferably 43.8.
３318.3 kA / m (550-4000 Oe), and the saturation magnetization value is 35-170 Am ² / kg (35-1
70 emu / g), more preferably 40 to 1
70Am a ^{2 / kg (40~170emu / g)} .

When cobalt-coated acicular iron oxide magnetic particle powder is used as the core particle powder, the coercive force value is 39.8 to 1
35.3 kA / m (500 to 1700 Oe) is preferred, and more preferably 42.8 to 135.3 kA / m (5
50 to 1700 Oe), and the saturation magnetization value is 60 to 9
^{0Am 2 / kg (60~90emu / g} ) are preferable,
More preferably, 65 to 90 Am ² / kg (65 to 90 e
mu / g). When the acicular metal magnetic particle powder containing iron as a main component and the acicular iron alloy magnetic particle powder are used as the core particle powder, the coercive force value is 63.7 to 278.5 kA / m.
(800-3500 Oe), more preferably 71.6-278.5 kA / m (900-3500 Oe).
e) wherein the saturation magnetization is 90-170 Am ² / kg
(90~170emu / g), more preferably 100~170Am ² / kg (100~170emu
/ G). When a plate-like magnetoplumbite type ferrite particle powder is used as the core particle powder, the coercive force value is 3
9.8 to 318.3 kA / m (500 to 4000 Oe)
Is preferable, and more preferably, 51.7 to 318.3 kA.
A / m (650~4000Oe), the saturation magnetization value ^{35~70Am 2 / kg (35~70emu / g} ) , more preferably 40~70Am ² / kg (40
７０70 emu / g).

In the composite magnetic particle powder according to the present invention, if necessary, the particle surface of the magnetic particle powder may be formed in advance by using at least one selected from hydroxides of aluminum, oxides of aluminum, hydroxides of silicon and oxides of silicon. It may be coated with one kind of intermediate coating, and the desorption of the phthalocyanine pigment from the particle surface of the magnetic particle powder can be further reduced as compared with the case where the coating is not performed with the intermediate coating.

The coating amount of the intermediate coating is 0.01 to 0.01 in terms of Al, SiO _2, or the sum of the Al conversion and the SiO ₂ conversion with respect to the magnetic particle powder coated with the intermediate coating.
-20% by weight is preferred.

If the amount is less than 0.01% by weight, the effect of reducing the desorption rate of the phthalocyanine pigment cannot be obtained.
The effect of reducing the desorption rate of the phthalocyanine-based pigment can be sufficiently obtained with the coating amount of 0.01 to 20% by weight, so that it is meaningless to cover more than 20% by weight more than necessary.

The composite magnetic particle powder according to the present invention 2 coated with the intermediate coating has almost the same particle size and geometry as the composite magnetic particle powder according to the present invention 1 not coated with the intermediate coating. It has a standard deviation value, a BET specific surface area value, a blackness L ^* value, magnetic properties, resin adsorption strength, and a phthalocyanine pigment desorption rate.

Further, the composite magnetic particle powder according to the present invention comprises:
If necessary, the surface of the magnetic particle powder may be coated with an intermediate coating and then subjected to carbon black adhesion treatment.

The composite magnetic particle powder according to the fourth aspect of the present invention has substantially the same particle size, geometric standard deviation, BET specific surface area, magnetic properties, and desorption of phthalocyanine pigments as the composite magnetic particle powder according to the second aspect of the present invention. Rate and resin adsorption strength. Further, the degree of blackness is almost the same as that of the composite magnetic particle powder according to the third aspect of the present invention.

Next, the magnetic recording medium according to the present invention will be described.

The magnetic recording medium according to the present invention comprises a non-magnetic support and a magnetic recording layer formed on the non-magnetic support and containing the composite magnetic particles according to the present invention and a binder resin.

Examples of the non-magnetic support include polyethylene terephthalate, polyethylene, polypropylene, polycarbonate, polyethylene naphthalate, polyamide, polyamide imide, and the like which are currently widely used for magnetic recording media.
Synthetic resin films such as polyimide, aluminum, and metal foils and plates such as stainless steel and various types of paper can be used, and the thickness thereof varies depending on the material, but is usually preferably 1.0 to 300 μm, more preferably 2.0 ~
200 μm.

In the case of a magnetic disk, polyethylene terephthalate is usually used as the nonmagnetic support, and its thickness is usually 50 to 300 μm, preferably 60 to 200 μm.
μm. In the case of a magnetic tape, in the case of polyethylene terephthalate, the thickness is usually 3 to 100 μm, preferably 4 to 20 μm, and in the case of polyethylene naphthalate, the thickness is usually 3 to 50 μm, preferably 4 to 2 μm.
0 μm, in the case of polyamide, the thickness is usually 2 to 10
μm, preferably 3 to 7 μm.

As binder resins, vinyl chloride-vinyl acetate copolymers, urethane resins, vinyl chloride-vinyl acetate-
Maleic acid copolymer, urethane elastomer, butadiene-acrylonitrile copolymer, polyvinyl butyral, cellulose derivatives such as nitrocellulose, polyester resin, synthetic rubber resin such as polybutadiene, epoxy resin, polyamide resin, polyisocyanate, electron beam curable acrylic Urethane resins and the like and mixtures thereof can be used.

Further, each binder resin has -OH, -COO
A polar group such as H, —SO ₃ M, —OPO ₂ M ₂ , and —NH ₂ (where M is H, Na, or K) may be included. Considering the dispersibility of the composite magnetic particle powder in the vehicle during the production of the magnetic paint, the polar group -COO
H, binder resin containing -SO ₃ M are preferable.

The coating thickness of the magnetic recording layer formed on the non-magnetic support is in the range of 0.01 to 5.0 μm. 0.
When the thickness is less than 01 μm, it is not preferable because uniform coating is difficult and uneven coating is likely to occur. If it exceeds 5.0 μm, it becomes difficult to obtain desired electromagnetic conversion characteristics due to the influence of a demagnetizing field. Preferably 0.05-4.0μ
m.

The mixing ratio of the composite magnetic particle powder and the binder resin in the magnetic recording layer is such that the composite magnetic particle powder is 5 to 2,000 parts by weight, preferably 100 to 1000 parts by weight, per 100 parts by weight of the binder resin. is there.

When the amount of the composite magnetic particles is less than 5 parts by weight, the amount of the composite magnetic particles in the magnetic paint is too small.
When a coating film is formed, a layer in which the composite magnetic particle powder is continuously dispersed cannot be obtained, and the smoothness of the coating film surface and the coating film strength become insufficient. If it exceeds 2000 parts by weight, the composite magnetic particle powder is not sufficiently dispersed in the magnetic paint because the amount of the composite magnetic particle powder is too large with respect to the amount of the binder resin. It is difficult to obtain a coating film having a sufficiently smooth surface. Further, since the composite magnetic particle powder is not sufficiently bound by the binder resin, the obtained coating film tends to be brittle.

It is to be noted that a known lubricant, an abrasive, an antistatic agent and the like used for the magnetic recording medium are required in the magnetic recording layer, and if necessary, about 0.1 to 50 parts by weight with respect to 100 parts by weight of the binder resin. May be included.

The magnetic recording medium according to the present invention is a composite magnetic particle according to the present invention, wherein cobalt-coated acicular iron oxide magnetic particle powder not coated with an intermediate coating is used as the core particle powder. When using powder,
The coercive force value is 39.8 to 135.3 kA / m (500 to 1
700 Oe), preferably 43.8 to 135.3 kA /
m (550-1700 Oe), squareness ratio (residual magnetic flux density B
r / saturated magnetic flux density Bm) is 0.85 to 0.95, preferably 0.86 to 0.95, and the glossiness of the coating film is 165 to 30.
0%, preferably 170-300%, coating surface roughness Ra
Is 11.0 nm or less, preferably 2.0 to 10.5 n
m, more preferably 2.0 to 10.0 nm, the Young's modulus is 125 to 160, preferably 126 to 160, and the linear absorption coefficient of the coating film is 1.20 to 5.0 μm ⁻¹ , preferably 1.
25～5.0Myuemu ^-1, running durability 21 minutes or more, preferably 22 minutes or more, A or B by abrasion characteristics infra evaluation method, preferably A.

The composite magnetic particles according to the present invention using, as the magnetic particle powder, a needle-like metal magnetic particle powder or a needle-like iron alloy magnetic particle powder mainly composed of iron which is not coated with an intermediate coating, as a core particle powder. When the powder is used, the coercive force value is 63.7 to 278.5 kA / m (800 to 35
00Oe), preferably 71.6 to 278.5 kA / m
(900-3500 Oe), squareness ratio (residual magnetic flux density Br)
/ Saturation magnetic flux density Bm) is 0.85-0.95, preferably 0.86-0.95, and the glossiness of the coating film is 185-300.
%, Preferably 190 to 300%, and the coating film surface roughness Ra is 11.0 nm or less, preferably 2.0 to 10.5 nm,
More preferably, 2.0 to 10.0 nm, Young's modulus is 12
5 to 160, preferably 126 to 160, and the film has a linear absorption coefficient of 1.30 to 5.0 μm ⁻¹ , preferably 1.35.
５5.0 μm ⁻¹ , running durability of 22 minutes or more, preferably 23 minutes or more, and abrasion characteristics of A or B, preferably A, according to the evaluation method described later.

The magnetic recording medium according to the present invention is characterized in that the composite magnetic particle powder according to the present invention using the plate-like magnetic particle powder not coated with the intermediate coating as the core particle powder as the magnetic particle powder. Indicates that the coercive force value is 39.8-
318.3 kA / m (500-4000 Oe), preferably 51.7-318.3 kA / m (650-4000)
Oe), squareness ratio (residual magnetic flux density Br / saturated magnetic flux density B)
m) is from 0.82 to 0.95, preferably from 0.83 to 0.
95, the glossiness of the coating film is 170 to 300%, preferably 175 to 300%, and the surface roughness Ra of the coating film is 11.
0 nm or less, preferably 2.0-10.5 nm, more preferably 2.0-10.0 nm, and the Young's modulus is 125-1.
60, preferably 126 to 160, and a linear absorption coefficient of the coating film of 1.25 to 5.0 μm ⁻¹ , preferably 1.25 to 5.
0 μm ⁻¹ , running durability is 22 minutes or more, preferably 23 minutes
Minutes or more, the scratch characteristics are A or B, preferably A according to the below-mentioned evaluation method.

When the composite magnetic particle powder according to the present invention using the acicular cobalt-coated iron oxide magnetic particle powder coated with the intermediate coating as the core particle powder is used as the magnetic particle powder, the coercive force Value is 39.8-135.3k
A / m (500-1700 Oe), preferably 43.8
135.3 kA / m (550-1700 Oe), and the squareness ratio (residual magnetic flux density Br / saturated magnetic flux density Bm) is 0.85
0.95, preferably 0.86-0.95, and the glossiness of the coating film is 170-300%, preferably 175-300.
%, The coating film surface roughness Ra is 10.0 nm or less, preferably 2.0 to 9.5 nm, more preferably 2.0 to 9.0 n.
m, Young's modulus is 127 to 160, preferably 128 to 1
60, the linear absorption coefficient of the coating film is 1.20 to 5.0 μm ⁻¹ ,
Preferably, it is 1.25 to 5.0 μm ⁻¹ , and the running durability is 2
The scratch characteristics are A or B, preferably A, according to the below-mentioned evaluation method for 2 minutes or more, preferably 23 minutes or more.

The composite magnetic particles according to the present invention using, as the magnetic particle powder, acicular metal magnetic particle powder or acicular iron alloy magnetic particle powder mainly composed of iron coated with an intermediate coating, as the core particle powder. When the powder is used, the coercive force value is 63.7 to 278.5 kA / m (800 to 350
0 Oe), preferably 71.6 to 278.5 kA / m.
(900-3500 Oe), squareness ratio (residual magnetic flux density Br)
/ Saturation magnetic flux density Bm) is 0.85 to 0.95, preferably 0.86 to 0.95, and the glossiness of the coating film is 190 to 300.
%, Preferably 195 to 300%, the coating film surface roughness Ra is 10.0 nm or less, preferably 2.0 to 9.5 nm, more preferably 2.0 to 9.0 nm, and the Young's modulus is 127 to
160, preferably 128 to 160, and the coating had a linear absorption coefficient of 1.30 to 5.0 μm ⁻¹ , preferably 1.35 to
5.0 μm ⁻¹ , running durability of 23 minutes or more, preferably 24 minutes or more,
Preferably it is A.

The magnetic recording medium according to the present invention uses, as the magnetic particle powder, the plate-like composite magnetic particle powder according to the present invention using the plate-like magnetic particle powder coated with the intermediate coating as the core particle powder. In this case, the coercive force value is 71.6.
３318.3 kA / m (500 to 4000 Oe), preferably 51.7 to 318.3 kA / m (650 to 400 Oe).
0 Oe), squareness ratio (residual magnetic flux density Br / saturated magnetic flux density B)
m) is from 0.82 to 0.95, preferably from 0.83 to 0.
95, the glossiness of the coating film is 175 to 300%, preferably 180 to 300%, and the surface roughness Ra of the coating film is 10.
5 nm or less, preferably 2.0 to 10.0 nm, more preferably 2.0 to 9.5 nm, and the Young's modulus is 126 to 16.
0, preferably 127 to 160, and a linear absorption coefficient of the coating film of 1.25 to 5.0 μm ⁻¹ , preferably 1.25 to 5.
0 μm ⁻¹ , running durability of 23 minutes or more, preferably 24
Minutes or more, the scratch characteristics are A or B, preferably A according to the below-mentioned evaluation method.

The magnetic recording medium according to the sixth aspect of the present invention has a non-magnetic underlayer containing non-magnetic particles and a binder resin between a non-magnetic support and a magnetic recording layer.

The non-magnetic particles for the non-magnetic underlayer include:
Usually, a nonmagnetic inorganic powder used for a nonmagnetic underlayer for a magnetic recording medium can be used. Specifically, hematite, hydrous iron oxide, titanium oxide, zinc oxide, tin oxide, tungsten oxide, silicon dioxide, α-alumina,
β-alumina, γ-alumina, chromium oxide, cerium oxide, silicon carbide, titanium carbide, silicon nitride, boron nitride, calcium carbonate, barium carbonate, magnesium carbonate, strontium carbonate, calcium sulfate, barium sulfate, molybdenum disulfide, titanium Barium acid or the like can be used alone or in combination, particularly, hematite,
Hydrous iron oxide, titanium oxide and the like are preferred.

In order to improve the dispersibility in the vehicle during the production of the non-magnetic paint, if necessary, the surface of the non-magnetic particle powder is treated with aluminum hydroxide, aluminum oxide, silicon hydroxide, The surface may be treated with an oxide of silicon or the like, and if necessary, to improve various characteristics such as light transmittance, surface electric resistance, mechanical strength, surface smoothness, and durability of the obtained magnetic recording medium. , A inside the particle
l, Ti, Zr, Mn, Sn, Sb and the like may be contained.

The non-magnetic particles include particles of various shapes, such as spherical, granular, octahedral, hexahedral, polyhedral, etc., needle-like, spindle-like, rice-granular, etc. There are plate-like particle powders and the like. Considering the surface smoothness of the obtained magnetic recording medium, the particle shape of the nonmagnetic particle powder is preferably acicular.

When the non-magnetic particle powder has a granular particle shape, the average particle diameter is 0.01 to 0.3 μm, preferably 0.015 to 0.25 μm, more preferably 0.02 to 0.2 μm. 2 μm, and when the particle shape is acicular,
The average major axis diameter is 0.01 to 0.3 μm, preferably 0.0
15 to 0.25 μm, more preferably 0.02 to 0.2
μm, and when the particle shape is plate-like, the average plate surface diameter is 0.1 μm.
01 to 0.3 μm, preferably 0.015 to 0.25 μm
m, more preferably 0.02 to 0.2 μm.

When the particle shape is acicular, the axial ratio is 2 to 2.
20, preferably 2.5 to 15, more preferably 3 to 1
0, when the particle shape is plate-like, the plate-like ratio is 2 to 50,
Preferably it is 2.5-20, More preferably, it is 3-10.

The nonmagnetic underlayer has a coating thickness of 0.2 to 1
A range of 0.0 μm is preferred. If it is less than 0.2 μm, it becomes difficult to improve the surface roughness of the non-magnetic support. In consideration of the thinning of the magnetic recording medium and the surface smoothness of the coating film, the thickness is more preferably in the range of 0.5 to 5.0 μm.

As the binder resin in the nonmagnetic underlayer, the binder resin used in forming the magnetic recording layer can be used.

The mixing ratio of the non-magnetic particle powder and the binder resin in the non-magnetic underlayer is 5 to 2000 parts by weight, preferably 100 to 1000 parts by weight, based on 100 parts by weight of the binder resin. is there.

When the amount of the non-magnetic particles is less than 5 parts by weight, the amount of the non-magnetic particles in the non-magnetic paint is too small.
When a coating film is formed, a layer in which a nonmagnetic particle powder is continuously dispersed cannot be obtained, and the smoothness of the coating film surface becomes insufficient. 200
When the amount exceeds 0 parts by weight, the nonmagnetic particle powder is not sufficiently dispersed in the nonmagnetic paint because the amount of the nonmagnetic particle powder is too large relative to the amount of the binder resin, and as a result, a coating film is formed. In this case, it is difficult to obtain a coating film having a sufficiently smooth surface. Further, since the nonmagnetic particle powder is not sufficiently bound by the binder resin, the obtained coating film tends to be brittle.

It is to be noted that a known lubricant, an abrasive, an antistatic agent and the like used for a magnetic recording medium are required for the non-magnetic underlayer to be 0.1 to 50 parts by weight based on 100 parts by weight of the binder resin.
It may be contained in an amount of about parts by weight.

The magnetic recording medium according to the sixth aspect of the present invention is a composite according to the present invention, wherein needle-like cobalt-coated iron oxide magnetic particles not coated with an intermediate coating are used as magnetic particles. When the magnetic particle powder is used, the coercive force value is 39.8 to 135.3 kA / m (50
0-1700 Oe), preferably 43.8-135.3.
kA / m (550-1700 Oe), squareness ratio (residual magnetic flux density Br / saturated magnetic flux density Bm) is 0.85-0.95,
Preferably 0.86 to 0.95, and the glossiness of the coating film is 170
To 300%, preferably 175 to 300%, and the coating film surface roughness Ra is 10.5 nm or less, preferably 2.0 to 10.
0 nm, more preferably 2.0 to 9.5 nm, the Young's modulus is 126 to 160, preferably 127 to 160, and the linear absorption coefficient of the coating film is 1.25 to 5.0 μm ⁻¹ , preferably 1.25 to 5 0.0 μm ⁻¹ , running durability of 22 minutes or more,
Preferably for at least 23 minutes, the abrasion characteristics are A or B, preferably A, according to the below-mentioned evaluation method.

As the magnetic particle powder, the composite magnetic particles according to the present invention using, as core particle powder, acicular metal magnetic particle powder or acicular iron alloy magnetic particle powder mainly composed of iron not covered with an intermediate coating. When the powder is used, the coercive force value is 63.7 to 278.5 kA / m (800 to 35
00Oe), preferably 71.6 to 278.5 kA / m
(900-3500 Oe), squareness ratio (residual magnetic flux density Br)
/ Saturation magnetic flux density Bm) is 0.85 to 0.95, preferably 0.86 to 0.95, and the glossiness of the coating film is 190 to 300.
%, Preferably 195 to 300%, and the coating film surface roughness Ra is 10.5 nm or less, preferably 2.0 to 10.0 nm,
More preferably, 2.0 to 9.5 nm, and Young's modulus is 126.
To 160, preferably 127 to 160, and a linear absorption coefficient of the coating film of 1.30 to 5.0 μm ⁻¹ , preferably 1.35 to
5.0 μm ⁻¹ , running durability of 23 minutes or more, preferably 24 minutes or more, and abrasion characteristics of A or B according to the evaluation method described later;
Preferably it is A.

In the case where the composite magnetic particle powder according to the present invention using the plate-like magnetic particle powder not coated with the intermediate coating as the core particle powder as the magnetic particle powder, the coercive force value is 39.8. ~ 318.3 kA / m (500
４4000 Oe), preferably 51.7 to 318.3 k
A / m (650-4000 Oe), squareness ratio (residual magnetic flux density Br / saturated magnetic flux density Bm) is 0.82-0.95, preferably 0.83-0.95, and the glossiness of the coating film is 175-300%, preferably 180-300%, and the surface roughness Ra of the coating film is 10.5 nm or less, preferably 2.0
１10.0 nm, more preferably 2.0 to 9.5 nm,
Young's modulus is 126 to 160, preferably 127 to 16
0, the linear absorption coefficient of the coating film is 1.25 to 5.0 μm ⁻¹ , preferably 1.25 to 5.0 μm ⁻¹ , and the running durability is 23.
Minutes or more, preferably 24 minutes or more, and the abrasion property is A or B, preferably A according to the evaluation method described later.

When the composite magnetic particle powder according to the present invention, in which the acicular cobalt-coated iron oxide magnetic particle powder coated with the intermediate coating is used as the core particle powder, the coercive force is increased. Value is 39.8-135.3k
A / m (500-1700 Oe), preferably 43.8
135.3 kA / m (550-1700 Oe), and the squareness ratio (residual magnetic flux density Br / saturated magnetic flux density Bm) is 0.85
0.95, preferably 0.86-0.95, and the glossiness of the coating film is 175-300%, preferably 180-300.
%, The coating film surface roughness Ra is 9.5 nm or less, preferably 2.0 to 9.0 nm, more preferably 2.0 to 8.5 n.
m, Young's modulus is 128 to 160, preferably 129 to 1
60, the linear absorption coefficient of the coating film is 1.20 to 5.0 μm ⁻¹ ,
Preferably, it is 1.25 to 5.0 μm ⁻¹ , and the running durability is 2
For at least 3 minutes, preferably at least 24 minutes, the abrasion characteristics are A or B, preferably A, according to the below-mentioned evaluation method.

An acicular composite according to the present invention using, as the magnetic particle powder, acicular metal magnetic particle powder or acicular iron alloy magnetic particle powder mainly composed of iron coated with an intermediate coating, as the core particle powder. When using magnetic particle powder,
The coercive force value is 63.7 to 278.5 kA / m (800 to 3
500 Oe), preferably 71.6 to 278.5 kA /
m (900-3500 Oe), squareness ratio (residual magnetic flux density B
r / saturation magnetic flux density Bm) is 0.85 to 0.95, preferably 0.86 to 0.95, and the glossiness of the coating film is 195 to 30.
0%, preferably 200-300%, coating film surface roughness Ra
Is 9.5 nm or less, preferably 2.0 to 9.0 nm, more preferably 2.0 to 8.5 nm, and the Young's modulus is 128 to
160, preferably 129 to 160, and the film has a linear absorption coefficient of 1.30 to 5.0 μm ⁻¹ , preferably 1.35 to
5.0 μm ⁻¹ , running durability of 24 or more, preferably 2
For 5 minutes or more, the scratch property is A or B, preferably A, according to the below-mentioned evaluation method.

When the composite magnetic particle powder according to the present invention using the plate-like magnetic particle powder coated with the intermediate coating as the core particle powder as the magnetic particle powder,
The coercive force value is 71.6 to 318.3 kA / m (500 to 4
000 Oe), preferably 51.7 to 318.3 kA /
m (650-4000 Oe), squareness ratio (residual magnetic flux density B
r / saturation magnetic flux density Bm) is 0.82 to 0.95, preferably 0.83 to 0.95, and the glossiness of the coating film is 18
0 to 300%, preferably 185 to 300%, and the surface roughness Ra of the coating film is 10.0 nm or less, preferably 2.0 to
9.5 nm, more preferably 2.0 to 9.0 nm, Young's modulus is 127 to 160, preferably 128 to 160, and the linear absorption coefficient of the coating film is 1.25 to 5.0 μm ⁻¹ , preferably 1.25. ５5.0 μm ⁻¹ , running durability of 24 minutes or more, preferably 25 minutes or more, and abrasion characteristics of A or B, preferably A, according to the evaluation method described later.

Next, a method for producing the composite magnetic particle powder according to the present invention will be described.

The magnetic particle powder to which the carbon black as the core particle powder in the present invention adheres is obtained by mixing the magnetic particle powder and alkoxysilane or polysiloxane, coating the particle surface of the magnetic particle powder with alkoxysilane or polysiloxane, Next, it can be obtained by mixing the magnetic particle powder coated with alkoxysilane or polysiloxane with the carbon black fine particle powder.

The coating of the magnetic particle powder with the alkoxysilane or polysiloxane may be performed by mechanically mixing and stirring the magnetic particle powder and the alkoxysilane solution or polysiloxane, or by mixing the magnetic particle powder with the alkoxysilane solution or polysiloxane. What is necessary is just to mix and stir mechanically while spraying polysiloxane. Almost all of the added alkoxysilane or polysiloxane is coated on the particle surface of the magnetic particle powder.

Incidentally, the coated alkoxysilane may be partially coated as an organosilane compound generated from the alkoxysilane generated through the coating step. Even in this case, there is no effect on the subsequent adhesion of the phthalocyanine pigment.

In order to uniformly coat the surface of the magnetic particle powder with the alkoxysilane or polysiloxane, it is preferable to previously disaggregate the magnetic particle powder using a pulverizer.

Examples of equipment for mixing and stirring magnetic particle powder and alkoxysilane or polysiloxane, and mixing and stirring a phthalocyanine pigment and magnetic particle powder having a particle surface coated with alkoxysilane or polysiloxane include powders. A device capable of applying a shearing force to the body layer is preferable, and in particular, a device capable of simultaneously performing shearing, spatula and compression, for example, a wheel-type kneader, a ball-type kneader,
A blade type kneader or a roll type kneader can be used. In practicing the present invention, a wheel-type kneader can be used more effectively.

Specific examples of the wheel type kneader include edge runners (synonyms for “mix miller”, “Simpson mill”, and “sand mill”), multimul, stots mill, wet pan mill, conner mill, and ring miller. And the like, preferably an edge runner, a multiple, a Stotts mill, a wet pan mill, and a ring muller, and more preferably an edge runner. Examples of the ball-type kneader include a vibration mill and the like. Specific examples of the blade type kneader include a Henschel mixer, a planetary mixer, and a Nauta mixer. Specific examples of the roll-type kneader include an extruder.

Magnetic particles that are easily oxidized such as magnetite particles, needle-like metal magnetic particles containing iron as a main component, and needle-like iron alloy magnetic particles are mixed with mixing equipment in order to prevent deterioration of magnetic properties due to oxidation. it is preferable to perform the purging and processing inert gas such as N ₂ in.

The conditions for mixing and stirring the magnetic particle powder and the alkoxysilane or polysiloxane are such that the linear load is 19.6 so that the alkoxysilane or polysiloxane is coated as uniformly as possible on the particle surface of the magnetic particle powder.
１９1960 N / cm (2 to 200 kg / cm), preferably 98 to 1470 N / cm (10 to 150 kg / c)
m), more preferably 147 to 980 N / cm (15 to 980 N / cm).
100 kg / cm), and the processing time may be appropriately adjusted within the range of 5 to 120 minutes, preferably 10 to 90 minutes. The stirring speed is 2 to 2000 rpm, preferably 5 to 1000 rpm, more preferably 10 to 800 rpm.
The processing conditions may be appropriately adjusted within the range of m.

The addition amount of the alkoxysilane or polysiloxane is 0.15 to 100 parts by weight of the magnetic particle powder.
45 parts by weight are preferred. With an addition amount of 0.15 to 45 parts by weight, 1 to 100 parts by weight of the phthalocyanine pigment can be attached to 100 parts by weight of the magnetic particle powder.

After coating the surface of the magnetic particles with alkoxysilane or polysiloxane, a phthalocyanine pigment is added, and the mixture is stirred to adhere the phthalocyanine pigment to the alkoxysilane coating or polysiloxane coating. If necessary, drying or heat treatment may be further performed.

The phthalocyanine pigment is preferably added little by little over time, especially over about 5 to 60 minutes.

The conditions for mixing and stirring are such that the linear load is 19.6 to 1 so that the phthalocyanine pigment is uniformly attached.
1960 N / cm (2-200 kg / cm), preferably 98-1470 N / cm (10-150 kg / c)
m), more preferably 147 to 980 N / cm (15 to 980 N / cm).
100 kg / cm), and the processing time may be appropriately adjusted within the range of 5 to 120 minutes, preferably 10 to 90 minutes. The stirring speed is 2 to 2000 rpm, preferably 5 to 1000 rpm, more preferably 10 to 800 rpm.
The processing conditions may be appropriately adjusted within the range of m.

The addition amount of the phthalocyanine pigment is 1 to 100 parts by weight based on 100 parts by weight of the magnetic particle powder.
If the amount of the phthalocyanine pigment is outside the above range, the desired composite magnetic particle powder cannot be obtained.

The heating temperature in the drying or heating treatment is usually preferably from 40 to 200 ° C., more preferably 6 to 200 ° C.
The heating time is preferably from 10 minutes to 12 hours, more preferably from 30 minutes to 3 hours.

The alkoxysilane used for coating the obtained composite magnetic particle powder is coated as an organosilane compound finally produced from the alkoxysilane through these steps.

If necessary, the magnetic particle powder may be prepared by preliminarily coating the particle surface of the magnetic particle powder with aluminum hydroxide,
It may be coated with one or more intermediate coatings selected from aluminum oxide, silicon hydroxide and silicon oxide.

The coating with the intermediate coating is carried out by adding an aluminum compound, a silicon compound or both compounds to an aqueous suspension obtained by dispersing the magnetic particle powder and mixing and stirring, or if necessary, mixing. By adjusting the pH value after stirring, the particle surface of the magnetic particle powder can be made of one or two selected from aluminum hydroxide, aluminum oxide, silicon hydroxide and silicon oxide.
Coated with at least one compound, then filtered, washed with water, dried,
Smash. If necessary, a deaeration / consolidation treatment may be performed.

As the aluminum compound, aluminum salts such as aluminum acetate, aluminum sulfate, aluminum chloride and aluminum nitrate, and alkali aluminates such as sodium aluminate can be used.

As the silicon compound, No. 3 water glass, sodium orthosilicate, sodium metasilicate and the like can be used.

Next, a method for manufacturing a magnetic recording medium according to the fifth and sixth embodiments of the present invention will be described.

The magnetic recording medium according to the fifth aspect of the present invention provides a magnetic recording medium comprising a non-magnetic support and a magnetic paint containing a composite magnetic particle powder, a binder resin and a solvent, formed on a non-magnetic support by a conventional method. Then, after calendering, it can be obtained by curing.

In the magnetic recording medium according to the sixth aspect of the present invention, a non-magnetic paint containing non-magnetic particles, a binder resin and a solvent is applied on a non-magnetic support and dried by a conventional method. Forming a composite magnetic particle powder on the non-magnetic underlayer,
It can be obtained by applying a magnetic paint containing a binder resin and a solvent to form a coating film, orienting in a magnetic field, performing a calendar treatment, and then curing.

For kneading and dispersing the magnetic paint and the non-magnetic paint, for example, a kneader may be a twin-screw kneader, a twin-screw extruder, a pressure kneader, a two-roll mill, a three-roll mill, or the like. , Ball mill,
Sand grinders, attritors, dispersers, homogenizers, ultrasonic dispersers and the like can be used.

In applying the magnetic paint and the non-magnetic paint, a gravure coater, a reverse roll coater, a slit coater, a die coater or the like can be used. The applied sheet can be oriented in a magnetic field by the orientation of a counter magnet, the orientation of a solenoid magnet, or the like.

As the solvent, there can be used methyl ethyl ketone, toluene, cyclohexanone, methyl isobutyl ketone, tetrahydrofuran, a mixture thereof and the like which are currently widely used for magnetic recording media.

The amount of the solvent used is 65 to 1000 parts by weight in total with respect to 100 parts by weight of the magnetic particle powder. 6
If the amount is less than 5 parts by weight, the viscosity becomes too high when a magnetic coating material is used, and application becomes difficult. If the amount exceeds 1000 parts by weight, the amount of the solvent volatilized when forming a coating film is too large, which is industrially disadvantageous.

[0142]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A typical embodiment of the present invention is as follows.
It is as follows.

The average particle diameter (average major axis diameter, average minor axis diameter, average plate surface diameter, average thickness, average particle diameter) of the magnetic particle powder, the composite magnetic particle powder, and the nonmagnetic particle powder is determined by electron micrograph. Approximately 350 particles shown in a photograph magnified 4 times in each of the vertical and horizontal directions were measured, and the average value was shown.

The axial ratio is indicated by the ratio between the average major axis diameter and the average minor axis diameter, and the plate ratio is indicated by the ratio between the average plate surface diameter and the average thickness.

The geometric standard deviation of the particle diameter of the particles was shown by the value obtained by the following method. That is, the value obtained by measuring the particle size of the particles shown in the above enlarged photograph, the particle size on the logarithmic normal probability paper in accordance with a statistical method from the actual particle size and the number of particles calculated from the measured value on the horizontal axis The particle size of
On the vertical axis, the cumulative number of particles (under the integrated screen) belonging to each of the predetermined particle diameter sections is plotted as a percentage.

The graph shows that the number of particles is 50.
% And 84.13% are read, and the geometric standard deviation value = 84.13% under the integrated screen.
And the value calculated according to the particle diameter (geometric mean diameter) at 50% under the integrated screen. The closer the geometric standard deviation value is to 1, the better the particle size distribution of the particles.

The specific surface area was indicated by a value measured by the BET method.

The amount of Al, the amount of Si existing inside or on the surface of the magnetic particles, the composite magnetic particles and the non-magnetic particles,
The amount of o, the amount of Ti and the amount of Ni, and the amount of Si contained in the organosilane compound generated from the alkoxysilane coated on the composite magnetic particle powder are respectively referred to as “X-ray fluorescence spectrometer 3063M” (Rigaku Corporation) JIS K0119 "General rules for X-ray fluorescence analysis"
It was measured according to.

The content of Fe ²⁺ in the magnetic particles was shown by the value obtained by the following chemical analysis method.

That is, under an inert gas atmosphere, 25 ml of a mixed solution containing phosphoric acid and sulfuric acid at a ratio of 2: 1 to 0.5 g of the magnetic particle powder was added to dissolve the magnetic particle powder. After adding a few drops of diphenylamine sulfonic acid as an indicator to the diluted solution of the dissolved aqueous solution, redox titration was performed using an aqueous solution of potassium dichromate. The end point was defined as the time when the diluted solution turned purple, and the amount was determined from the amount of the aqueous potassium dichromate solution used up to the end point.

The phthalocyanine pigment adhering to the composite magnetic particle powder is described in “HORIBA Metal Carbon / Sulfur Analyzer EMI
A-2200 type "(manufactured by Horiba, Ltd.) and the amount of carbon was measured.

The blackness of the acicular magnetic particle powder, the composite magnetic particle powder and the non-magnetic particle powder was determined by kneading a sample (0.5 g) and castor oil (1.5 ml) with a Hoover-type muller into a paste. Add 4.5 g,
After kneading and coating, 150 μm (6
mil) was applied using an applicator (mil: mil) and the coating piece was prepared using a multi-source spectrophotometer MSC-IS-2D (manufactured by Suga Test Instruments Co., Ltd.). The measurement was carried out and represented by a color index L ^* according to JIS Z 8729.

Here, the L ^* value represents lightness, and the smaller the L ^* value, the better the blackness.

The desorption rate (%) of the phthalocyanine pigment adhering to the composite magnetic particles was shown by the value obtained by the following method. The closer the detachment rate of the phthalocyanine pigment is to 0%, the smaller the detachment amount of the phthalocyanine pigment from the particle surface of the composite magnetic particle powder is.

3 g of composite magnetic particle powder and 40 m of ethanol
was placed in a 50 ml sedimentation tube, subjected to ultrasonic dispersion for 20 minutes, and allowed to stand still for 120 minutes to separate the composite magnetic particle powder and the detached phthalocyanine pigment according to the sedimentation speed.
Next, 40 m of ethanol was added to the composite magnetic particle powder again.
After adding ultrasonic dispersion for 20 minutes, the mixture was allowed to stand for 120 minutes to separate the composite magnetic particle powder and the separated phthalocyanine pigment. The composite magnetic particle powder was dried at 80 ° C. for 1 hour, the amount of the phthalocyanine pigment was measured, and the value obtained according to the following equation 1 was defined as the desorption rate (%) of the phthalocyanine pigment.

[0156]

## EQU1 ## Desorption rate (%) of phthalocyanine pigment = 顔料 (W
a-We) / Wa｝ × 100 Wa: Attached amount of phthalocyanine pigment to composite magnetic particle powder We: Attached amount of phthalocyanine pigment to composite magnetic particle powder after desorption test

The resin adsorption strength indicates the degree to which the resin is adsorbed on the particle powder. The closer the resin adsorption strength obtained by the following method is to 100%, the more strongly the resin is adsorbed on the particle surface. Is shown.

First, the resin adsorption amount Ya is determined.

A mixed solvent (27.0 g of methyl ethyl ketone, 16.1 g of toluene) in which 20 g of the particles to be measured and 2 g of a polyurethane resin having a sodium sulfonate group were dissolved.
2g, cyclohexanone 10.8g) 56g and 3mm
Put into a 100 ml poly bottle together with 120 g of φ steel beads, and mix and disperse with a paint shaker for 60 minutes.

Next, 50 g of this coating composition was taken out and the
The mixture is placed in a 0 ml settling tube and centrifuged at 10,000 rpm for 15 minutes to separate a solid portion and a solvent portion.
Then, the concentration of the resin solid content contained in the solvent portion is quantified by a gravimetric method, and the amount of the resin present in the solid portion is obtained by subtracting the concentration from the charged resin amount. ).

Next, only the previously separated solid portion was
The whole amount was taken out into a 2 ml tall beaker, and mixed solvent (25.0 g of methyl ethyl ketone, 15.0 ml of toluene)
g, cyclohexanone 10.0 g) and 50 g.
After ultrasonic dispersion for a minute, the suspension is put into a 50 ml sedimentation tube and centrifuged at 10,000 rpm for 15 minutes to separate a solid portion and a solvent portion. Then, by measuring the resin solid content concentration in the solvent portion, the amount of resin extracted into the solvent phase among the resin adsorbed on the particle surface is quantified.

Further, the operation from the removal of the total amount of only the solid portion into a 100 ml tall beaker to the determination of the amount of the resin dissolved in the solvent phase was repeated twice, and the total amount of the resin extracted in the solvent phase was totaled three times. Ye (mg / g) was determined, and the value determined according to the following equation 2 was defined as the resin adsorption strength (%).

[0163]

## EQU2 ## Resin adsorption strength (%) = [(Ya-Ye) / Y
a) × 100

The magnetic characteristics of the magnetic particle powder, the composite magnetic particle powder and the magnetic recording medium are described in “Vibration sample magnetometer VSM-3”.
S-15 "(manufactured by Toei Industry Co., Ltd.)
95.8 kA / m (10 kOe) (however, 39.79 kA when cobalt-coated magnetic iron oxide particles are used)
/ M (5 kOe)), and various characteristics of the magnetic tape are determined by an external magnetic field of 795.8 kA / m (10 kOe).
e) (However, when cobalt-coated magnetic iron oxide particle powder is used as the magnetic particle powder, 39.79 kA / m (5
kOe)).

The coating viscosity was determined by measuring the coating viscosity of the obtained magnetic coating at 25 ° C. using an E-type viscometer EMD-R (manufactured by Tokyo Keiki Co., Ltd.), and the shear rate D = 1.92 sec.
It was shown by the value at c ^{- 1} .

The glossiness of the coating film surface of the magnetic recording layer was determined by measuring the 45 ° glossiness of the coating film using “Gloss Meter UGV-5D” (manufactured by Suga Test Instruments Co., Ltd.).

The surface roughness Ra is calculated as follows: Surfcom-57
The center line average roughness of the coating film was measured using “5A” (manufactured by Tokyo Seimitsu Co., Ltd.).

The strength of the coating film was determined by measuring the Young's modulus of the coating film using “Autograph” (manufactured by Shimadzu Corporation). Young's modulus was measured using a commercially available video tape "AV T-120".
(Manufactured by Victor Company of Japan, Ltd.) ". The higher the relative value, the better the coating film strength.

The degree of light transmission is described in “Self-Recording Photoelectric Spectrophotometer U
V-2100 "(manufactured by Shimadzu Corporation) was used as the linear absorption coefficient calculated by inserting the value of the light transmittance of the magnetic recording medium into Equation 3 below. The larger the linear absorption coefficient is, the harder it is to transmit light.

In measuring the light transmittance, the same non-magnetic support as the non-magnetic support used for the magnetic recording medium was used as a blank.

[0171]

## EQU3 ## Linear absorption coefficient (μm ⁻¹ ) = [ln (1 / t)] / FT t: light transmittance at λ = 900 nm (−) FT: film thickness of magnetic recording layer (μm)

The running durability of the magnetic recording medium is as follows:
a Durability Tester MDT-3
000 "(Steinberg Associates
(Manufactured by the company), and the actual operation time at a load of 1.96 N (200 gw) and a relative speed of 16 m / s between the head and the tape was evaluated. The longer the actual operating time, the better the running durability.

The scratch characteristics were evaluated by observing the surface of the tape after running with a microscope and visually evaluating the presence or absence of scratches.
A rating was given on a scale.

A: No abrasion B: Some abrasion C: Abrasion D: Severe abrasion

The thickness of each of the non-magnetic support, the non-magnetic underlayer, and the magnetic recording layer constituting the magnetic recording medium was measured as follows.

Digital electronic micrometer K351C
First, the film thickness (A) of the nonmagnetic support is measured using (manufactured by Anritsu Electric Co., Ltd.). Next, the thickness (B) of the nonmagnetic support and the nonmagnetic underlayer formed on the nonmagnetic support
(Sum of the thickness of the nonmagnetic support and the thickness of the nonmagnetic underlayer)
Is measured in the same manner.

Further, the thickness (C) of the magnetic recording medium obtained by forming the magnetic recording layer on the nonmagnetic underlayer (the thickness of the nonmagnetic support, the thickness of the nonmagnetic underlayer, and the thickness of the magnetic recording layer) Is calculated in the same manner. The thickness of the nonmagnetic underlayer is shown by (B)-(A), and the thickness of the magnetic recording layer is shown by (C)-(B).

The thickness of each layer of the magnetic recording medium having no nonmagnetic underlayer is determined by measuring the thickness (A) of the nonmagnetic support and the thickness (C) of the magnetic recording medium. Was determined as (C)-(A).

<Production of Composite Magnetic Particle Powder> Acicular cobalt-coated magnetite particle powder containing 1.83% by weight of cobalt with respect to the magnetic particle powder and 15.3% by weight of Fe ²⁺ with respect to the magnetic particle powder ( Average major axis diameter 0.251 μm,
Axial ratio 8.0, geometric standard deviation 1.38, BET specific surface area 38.5 m ² / g, blackness L ^* value 23.1, resin adsorption strength 48.2%, coercive force value 55.0 kA / m (691O
e), saturation magnetization value of 80.6 Am ^{2 /} kg (80.6 em
u / g)) In order to disperse the coagulation, 20 kg of the water are brought into contact with 150 l of pure water using a stirrer, and further passed through "TK Pipeline Homogenizer" (product name, manufactured by Tokushu Kika Kogyo Co., Ltd.) three times. Thus, a slurry containing acicular cobalt-coated magnetite particles was obtained.

Next, the slurry containing the acicular cobalt-coated magnetite particle powder was subjected to a horizontal sand grinder “Mighty Mill MHG-1.5L” (product name, manufactured by Inoue Seisakusho Co., Ltd.) at a shaft rotation speed of 2000 rpm for 5 minutes. The dispersion was passed twice to obtain a dispersion slurry containing acicular cobalt-coated magnetite particle powder.

The obtained dispersion slurry was 325 mesh
The sieve residue at (opening 44 μm) was 0%. The dispersion slurry was separated by filtration and washed with water to obtain a cake of acicular cobalt-coated magnetite particle powder. After drying the cake of the acicular cobalt-coated magnetite particle powder at 120 ° C., 11.0 kg of the dried powder is transferred to an edge runner “MPU
V-2 "(product name, manufactured by Matsumoto Casting Ironworks Co., Ltd.) and 392 N / c while blowing 2 l of nitrogen per minute.
The mixture was stirred at m (40 Kg / cm) for 15 minutes to loosen the aggregation of particles.

Next, 220 g of methyltriethoxysilane
Was added and mixed with 200 ml of ethanol, and a methyltriethoxysilane solution obtained was added to the above-mentioned acicular cobalt-coated magnetite particle powder in which the agglomeration of the particles was released while operating the edge runner, and 294 N / cm (3
(0 Kg / cm) and the mixture was stirred for 20 minutes.

Next, 1100 g of phthalocyanine pigment A (particle shape: granular, average particle diameter 0.06 μm, BET specific surface area value 680 m ² / g, blackness L ^* value 17.7)
Was added over a period of 10 minutes while operating the edge runner, and further mixed and stirred at a line load of 294 N / cm (30 Kg / cm) for 30 minutes to attach the phthalocyanine pigment to the methyltriethoxysilane coating. Heat treatment was performed at 80 ° C. for 120 minutes using a dryer to obtain acicular composite magnetic particle powder. The stirring speed at this time is 22r
pm.

The obtained acicular composite magnetic particle powder has an average length.
The shaft diameter was 0.252 μm, and the shaft ratio was 8.0. Geometric marker
The quasi-deviation is 1.38 and the BET specific surface area is 39.
6m ²/ G, blackness L^*The value is 19.8 and the resin adsorption strength is
78.0%, the desorption rate of the phthalocyanine pigment is 6.9
%, Coercive force value is 54.5 kA / m (685 Oe), saturation
Magnetization value is 77.0 Am²/ Kg (77.0 emu / g)
Is an organo-organic compound formed from methyltriethoxysilane.
The coating amount of the silane compound is 0.31% by weight in terms of Si,
The amount of the attached phthalocyanine-based pigment is 6.
03% by weight (acicular cobalt-coated magnetite particle powder 1
(Corresponding to 10 parts by weight with respect to 00 parts by weight).
As a result of electron microscopic observation, almost no phthalocyanine pigment
Phthalocyanine pigments
All amount adhered to the methyltriethoxysilane coating layer
It was recognized that.

<Production of magnetic recording medium> 12 g of the acicular composite magnetic particle powder obtained above and an abrasive (trade name: AKP-
30, Sumitomo Chemical Co., Ltd.) 1.2 g, carbon black (trade name: # 2400B, manufactured by Mitsubishi Kasei Corporation).
06 g, a binder resin solution (30% by weight of a vinyl chloride-vinyl acetate copolymer resin having a sodium sulfonate group and 70% by weight of cyclohexanone) and cyclohexanone were mixed to obtain a mixture (solid content: 78%). Was further kneaded with a plast mill for 30 minutes to obtain a kneaded material.

The kneaded material was placed in a 140 ml glass bottle for 1.5 times.
95 g of mmφ glass beads, additional binder resin solution (30% by weight of polyurethane resin having sodium sulfonate group, solvent (methyl ethyl ketone: toluene = 1: 1)) 7
0% by weight), cyclohexanone, methyl ethyl ketone and toluene, and mixed and dispersed for 6 hours with a paint shaker to obtain a magnetic paint. Thereafter, a lubricant and a curing agent were added, and the mixture was further mixed and dispersed with a paint shaker for 15 minutes.

The composition of the obtained magnetic paint was as follows. Acicular composite magnetic particle powder 100 parts by weight Vinyl chloride-vinyl acetate copolymer resin having sodium sulfonate group 10 parts by weight Polyurethane resin having sodium sulfonate group 10 parts by weight Abrasive (AKP-30) 10 parts by weight Carbon black ( # 2400B) 0.5 parts by weight Lubricant (myristic acid: butyl stearate = 1: 2) 3.0 parts by weight Curing agent (polyisocyanate) 5.0 parts by weight Cyclohexanone 65.8 parts by weight Methyl ethyl ketone 164.5 parts by weight 98.7 parts by weight of toluene

The viscosity of the obtained magnetic paint was 2,848.
cP.

The obtained magnetic paint was applied on a polyethylene terephthalate film having a thickness of 12 μm using an applicator to a thickness of 45 μm, and then oriented and dried in a magnetic field.
For 24 hours, and slit to a width of 1.27 cm (0.5 inch) to obtain a magnetic tape. The thickness of the magnetic recording layer was 3.5 μm.

The resulting magnetic tape had a coercive force value of 56.
8 kA / m (714 Oe), squareness ratio (Br / Bm) of 0.89, glossiness of 178%, and surface roughness Ra of 6.6 n
m, Young's modulus (relative value) is 141, and linear absorption coefficient is 1.3.
6 cm ⁻¹ , of which the running durability is 28.3 minutes,
The scratch characteristics were A.

[0191]

In the present invention, the most important point is that the particle surface of the magnetic particle powder is coated with an organosilane compound or polysiloxane formed from alkoxysilane, and a phthalocyanine pigment is adhered to the coating. This is a fact that the magnetic particle powder has high resin adsorption strength and excellent dispersibility.

The reason for the high resin adsorption strength of the composite magnetic particle powder according to the present invention is that the present inventor attaches a phthalocyanine pigment to the particle surface of the magnetic particle powder via an organosilane compound or polysiloxane. It is believed that the presence of a phthalocyanine pigment having a benzene ring on the particle surface of the composite magnetic particle powder improved the compatibility with the resin, especially with the polyurethane resin commonly used for magnetic recording media. I have.

Regarding the reason why the composite magnetic particle powder according to the present invention is excellent in dispersibility, the present inventor has proposed that the phthalocyanine pigment desorbed from the particle surface of the composite magnetic particle powder is small, and that the It is considered that the dispersion in the system is not hindered by the pigment, and that the phthalocyanine-based pigment adheres to the particle surface of the magnetic particle powder, so that irregularities are generated on the particle surface and the contact between particles is suppressed.

A magnetic recording medium having a magnetic recording layer using the composite magnetic particle powder according to the present invention has excellent durability and sufficient surface smoothness. It is considered that the reason why the durability is excellent is that the compatibility with the resin used for the magnetic recording medium is improved by the improvement of the resin adsorption strength of the composite magnetic particle powder as described above.
In addition, the reason why the surface smoothness is excellent is that the organosilane compound or polysiloxane to which the phthalocyanine pigment is adhered is strongly bonded to the particle surface of the magnetic particle powder, so that the particle surface of the composite magnetic particle powder is The phthalocyanine-based pigment detached from the pigment decreases, and as a result, the dispersion of the composite magnetic particle powder in the vehicle is not hindered, and the dispersibility of the composite magnetic particle powder itself is improved, so that the surface smoothness of the magnetic recording layer is improved. The present inventor believes that this is due to the improvement.

[0195]

Next, examples and comparative examples will be described.

Core particles 1 to 7: Various magnetic particle powders obtained by a known production method were prepared.

Table 1 shows the properties of the magnetic particle powder.

[0198]

[Table 1]

Core Particles 8 The pH value of 150 l of pure water was adjusted to 11.0 using an aqueous sodium hydroxide solution, and 20 kg of needle-like metal magnetic particles containing iron as a main component (core particles 1) were added. Then, the mixture was passed through a homomic line mill (manufactured by Tokushu Kika Kogyo Co., Ltd.) three times to obtain a slurry of powder of acicular metal magnetic particles containing iron as a main component.

After adjusting the concentration of the slurry to 98 g / l by adding water to the slurry, 150 liters were withdrawn from the slurry and heated to 60 ° C. with stirring.

5444 ml of a 1.0 mol / l aqueous solution of sodium aluminate (1.0% by weight in terms of Al with respect to the needle-like metal magnetic particles containing iron as a main component) was added to the slurry.
Was added and the mixture was kept for 30 minutes and then adjusted to pH 8.5 with acetic acid.

After maintaining in this state for 30 minutes, filtration, washing with water, and drying and pulverization while purging with N ₂ gas, a needle mainly composed of iron whose particle surface is coated with aluminum hydroxide is used. A metallic magnetic particle powder was obtained.

The production conditions at this time are shown in Table 2, and various properties of the obtained needle-like metal magnetic particle powder containing iron as a main component whose surface is coated with an intermediate coating are shown in Table 3.

The type A of the coating in the surface treatment step is an aluminum hydroxide, and S is an oxide of silicon.

[0205]

[Table 2]

[0206]

[Table 3]

Core Particles 9 to 11 Magnetic particles coated with an intermediate coating were obtained in the same manner as for the core particles 8, except that the types of the core particles and the types and amounts of additives in the surface treatment step were variously changed.

The processing conditions at this time are shown in Table 2, and various properties of the magnetic particle powder coated with the obtained intermediate coating are shown in Table 3.

Phthalocyanine pigments A to C: Phthalocyanine pigments A to C having the properties shown in Table 4 were prepared.

[0210]

[Table 4]

Examples 1 to 11 and Comparative Examples 1 to 4: Types of core particle powder, types and amounts of additives in coating step with alkoxysilane and polysiloxane, treatment conditions with edge runner, adhesion step of phthalocyanine pigment The composite magnetic particle powder was obtained in the same manner as in the embodiment of the present invention, except that the type and amount of the phthalocyanine pigment and the processing conditions with the edge runner were variously changed. The composite magnetic particle powder obtained in each of Examples 1 to 11 shows almost no phthalocyanine-based pigment as a result of electron microscopic observation. It was confirmed that it adhered to the compound coating or the polysiloxane coating.

Table 5 shows the processing conditions and Table 6 shows the properties of the obtained composite magnetic particles.

[0213]

[Table 5]

[0214]

[Table 6]

<Manufacture of Magnetic Recording Medium> Examples 12 to 22 and Comparative Examples 5 to 10 A magnetic recording medium was obtained in the same manner as in the embodiment of the present invention, except that the type of the magnetic particle powder was variously changed. .

Table 7 shows the manufacturing conditions and various characteristics at this time.

[0219]

[Table 7]

<Production of Non-Magnetic Underlayer> Non-magnetic particles 1 to 6 Table 8 shows various characteristics of various non-magnetic particle powders.

[0219]

[Table 8]

Underlayer 1 12 g of the hematite particles of the nonmagnetic particles 1 were mixed with a binder resin solution (30% by weight of a vinyl chloride-vinyl acetate copolymer resin having a sodium sulfonate group and 70% by weight of cyclohexanone) and cyclohexanone. Thus, a mixture (solid content: 72%) was obtained, and the mixture was further kneaded with a plastmill for 30 minutes to obtain a kneaded product.

This kneaded material was mixed with 1.5 mmφ glass beads 9
5 g, additional binder resin solution (30% by weight of polyurethane resin having sodium sulfonate group, 70% by weight of solvent (methyl ethyl ketone: toluene = 1: 1)), cyclohexanone, methyl ethyl ketone and toluene were added to a 140 ml glass bottle, and a paint shaker was added. At 6
Mixing and dispersion were performed for a time to obtain a coating composition. Thereafter, a lubricant was added, and the mixture was further mixed and dispersed with a paint shaker for 15 minutes.

The composition of the obtained nonmagnetic paint was as follows.

Non-magnetic particle powder 100 parts by weight Vinyl chloride-vinyl acetate copolymer resin having sodium sulfonate group 10 parts by weight Polyurethane resin having sodium sulfonate group 10 parts by weight Lubricant (myristic acid: butyl stearate = 1: 1) 1) 2 parts by weight Cyclohexanone 56.9 parts by weight Methyl ethyl ketone 142.3 parts by weight Toluene 85.4 parts by weight

Next, the above-mentioned non-magnetic paint was applied on a polyethylene terephthalate film having a thickness of 12 μm using a slit coater, and then dried to form a non-magnetic underlayer.

Table 9 shows the manufacturing conditions and various characteristics of the obtained nonmagnetic underlayer.

[0226]

[Table 9]

Underlayers 2 to 6 Nonmagnetic underlayers were obtained in the same manner as underlayer 1 except that the type of nonmagnetic particle powder was changed in various ways.

Table 9 shows the manufacturing conditions and various characteristics of the obtained nonmagnetic underlayer.

<Production of Magnetic Recording Medium Having Non-Magnetic Underlayer> Example 23 Using the composite magnetic particle powder of Example 1, a magnetic paint was obtained in the same manner as in the embodiment.

After applying a magnetic paint to a thickness of 15 μm on the underlayer 1 using an applicator, orienting and drying in a magnetic field, and then performing a calendering treatment,
A curing reaction was performed at 0 ° C. for 24 hours, and slit to a width of 1.27 cm (0.5 inch) to obtain a magnetic tape.

Table 10 shows the manufacturing conditions and various characteristics of the obtained magnetic recording medium.

Examples 24 to 33 and Comparative Examples 11 to 16 Magnetic recording media were obtained in the same manner as in Example 23 except that the type of the nonmagnetic underlayer and the type of the magnetic particles were variously changed.

Table 10 shows the manufacturing conditions and various characteristics of the obtained magnetic recording medium.

[0234]

[Table 10]

[0235]

The composite magnetic particles according to the present invention have high blackness and resin adsorption strength and are excellent in dispersibility, so that a magnetic recording medium having excellent strength and durability can be obtained. It is suitable as a magnetic particle powder for a magnetic recording medium.

As described above, the magnetic recording medium according to the present invention is excellent in strength and durability due to the fact that the composite magnetic particle powder has excellent resin adsorption strength. It is preferable as a medium.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroko Morii 1-4, Meiji Shinkai, Otake City, Hiroshima Prefecture F-term in Otake Creative Center, Toda Kogyo Co., Ltd. 4G002 AA06 AA12 AB05 AD02 AE03 5D006 BA07 BA08 FA00 5E040 AA19 AB01 BC01 CA01 CA06 HB14 HB17 NN01 NN05 NN06 NN12

Claims (6)

[Claims] 1. An average particle diameter of a magnetic particle powder comprising a magnetic particle powder having a particle surface coated with an organosilane compound or polysiloxane formed from alkoxysilane, and a phthalocyanine pigment adhered to at least a part of the coating.
2 to 0.70 μm composite magnetic particle powder, wherein the amount of the phthalocyanine pigment attached is
The composite magnetic particle powder for a magnetic recording medium is 1 to 100 parts by weight with respect to parts by weight. 2. The intermediate coating according to claim 1, wherein the surface of the magnetic particle powder is at least one selected from the group consisting of aluminum hydroxide, aluminum oxide, silicon hydroxide and silicon oxide. Composite magnetic particle powder for a magnetic recording medium, wherein the composite magnetic particle powder is coated with a magnetic recording medium. 3. The particle surface is coated with an organosilane compound or a polysiloxane formed from an alkoxysilane, and the coating is coated with carbon black. Further, an organosilane compound formed from the alkoxysilane on the carbon black or The polysiloxane is coated, and the phthalocyanine pigment is adhered to at least a part of the coating.
2 to 0.70 μm composite magnetic particle powder, wherein the amount of the phthalocyanine pigment attached is
The composite magnetic particle powder for a magnetic recording medium is 1 to 100 parts by weight with respect to parts by weight. 4. The intermediate coating according to claim 3, wherein the particle surface of the magnetic particle powder comprises at least one selected from the group consisting of aluminum hydroxide, aluminum oxide, silicon hydroxide and silicon oxide. Composite magnetic particle powder for a magnetic recording medium, wherein the composite magnetic particle powder is coated with a magnetic powder. 5. A magnetic recording medium comprising a non-magnetic support, a magnetic recording layer containing a magnetic particle powder formed on the non-magnetic support and a binder resin, wherein the magnetic particle powder is used. 5. A magnetic recording medium comprising the composite magnetic particle powder according to claim 4. 6. A non-magnetic support, a non-magnetic underlayer containing a non-magnetic particle powder formed on the non-magnetic support and a binder resin, and bonding to a magnetic particle powder formed on the non-magnetic under layer 5. A magnetic recording medium comprising a magnetic recording layer containing a dispersing agent resin, wherein the magnetic particle powder is the composite magnetic particle powder according to any one of claims 1 to 4.